Dams

Dams are obstructions built across rivers or streams to hold back water, creating reservoirs. They serve multiple aims: water supply for domestic and industrial use, irrigation, flood control, hydroelectric power generation, and recreational or ecological benefits.

Dams vary by design and materials. Common types include gravity dams, which use their weight to resist forces; arch dams, which transfer load to abutments; buttress dams, which use a series of supports; and embankment dams, typically earthfill or rockfill. Construction materials range from reinforced concrete to compacted earth and rock. Many dams include spillways, intake structures, and outlet works to manage inflow and water release.

Design considerations include foundation conditions, seepage control, structural stability, environmental and seismic risks, sediment management, and downstream flow requirements. Operational aspects include reservoir level management, turbine intake gates for hydroelectric plants, and maintenance of safety features. Regulatory oversight and dam safety organizations monitor integrity and update standards.

Environmental and social impacts can be significant. Reservoir creation may displace communities, alter habitats, affect fish migration, and trap sediments, reducing reservoir capacity over time. Downstream flows and water temperatures can change, influencing ecosystems. Mitigation measures include fish ladders, sediment management, and careful planning of discharge regimes.

Dams have a long history, with early masonry and earthworks in ancient civilizations. The modern era saw large-scale concrete gravity and arch dams for navigation, water supply, and power. Notable examples include the Hoover Dam, the Aswan High Dam, the Three Gorges Dam, and the Itaipu and Glen Canyon projects. The global dam landscape continues to evolve with debates over safety, ecological impact, and climate resilience.